/*
 * 09/26/08     throw exception on subbband alloc error: Christopher G. Jennings (cjennings@acm.org)
 * 
 * 11/19/04		1.0 moved to LGPL.
 * 
 * 12/12/99		Initial version. Adapted from javalayer.java
 *				and Subband*.java. mdm@techie.com
 *
 * 02/28/99		Initial version : javalayer.java by E.B
 *-----------------------------------------------------------------------
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU Library General Public License as published
 *   by the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU Library General Public License for more details.
 *
 *   You should have received a copy of the GNU Library General Public
 *   License along with this program; if not, write to the Free Software
 *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *----------------------------------------------------------------------
 */

package javazoom.jl.decoder;

/**
 * Implements decoding of MPEG Audio Layer I frames.
 */
class LayerIDecoder implements FrameDecoder {
	protected Bitstream stream;
	protected Header header;
	protected SynthesisFilter filter1, filter2;
	protected Obuffer buffer;
	protected int which_channels;
	protected int mode;

	protected int num_subbands;
	protected Subband[] subbands;
	protected Crc16 crc = null; // new Crc16[1] to enable CRC checking.

	public LayerIDecoder() {
		crc = new Crc16();
	}

	public void create(Bitstream stream0, Header header0, SynthesisFilter filtera, SynthesisFilter filterb,
			Obuffer buffer0, int which_ch0) {
		stream = stream0;
		header = header0;
		filter1 = filtera;
		filter2 = filterb;
		buffer = buffer0;
		which_channels = which_ch0;

	}

	public void decodeFrame() throws DecoderException {

		num_subbands = header.number_of_subbands();
		subbands = new Subband[32];
		mode = header.mode();

		createSubbands();

		readAllocation();
		readScaleFactorSelection();

		if ((crc != null) || header.checksum_ok()) {
			readScaleFactors();

			readSampleData();
		}

	}

	protected void createSubbands() {
		int i;
		if (mode == Header.SINGLE_CHANNEL)
			for (i = 0; i < num_subbands; ++i)
				subbands[i] = new SubbandLayer1(i);
		else if (mode == Header.JOINT_STEREO) {
			for (i = 0; i < header.intensity_stereo_bound(); ++i)
				subbands[i] = new SubbandLayer1Stereo(i);
			for (; i < num_subbands; ++i)
				subbands[i] = new SubbandLayer1IntensityStereo(i);
		} else {
			for (i = 0; i < num_subbands; ++i)
				subbands[i] = new SubbandLayer1Stereo(i);
		}
	}

	protected void readAllocation() throws DecoderException {
		// start to read audio data:
		for (int i = 0; i < num_subbands; ++i)
			subbands[i].read_allocation(stream, header, crc);

	}

	protected void readScaleFactorSelection() {
		// scale factor selection not present for layer I.
	}

	protected void readScaleFactors() {
		for (int i = 0; i < num_subbands; ++i)
			subbands[i].read_scalefactor(stream, header);
	}

	protected void readSampleData() {
		boolean read_ready = false;
		boolean write_ready = false;
		int mode = header.mode();
		int i;
		do {
			for (i = 0; i < num_subbands; ++i)
				read_ready = subbands[i].read_sampledata(stream);
			do {
				for (i = 0; i < num_subbands; ++i)
					write_ready = subbands[i].put_next_sample(which_channels, filter1, filter2);

				filter1.calculate_pcm_samples(buffer);
				if ((which_channels == OutputChannels.BOTH_CHANNELS) && (mode != Header.SINGLE_CHANNEL))
					filter2.calculate_pcm_samples(buffer);
			} while (!write_ready);
		} while (!read_ready);

	}

	/**
	 * Abstract base class for subband classes of layer I and II
	 */
	abstract static class Subband {
		/*
		 * Changes from version 1.1 to 1.2: - array size increased by one, although a
		 * scalefactor with index 63 is illegal (to prevent segmentation faults)
		 */
		// Scalefactors for layer I and II, Annex 3-B.1 in ISO/IEC DIS 11172:
		public static final float scalefactors[] = { 2.00000000000000f, 1.58740105196820f, 1.25992104989487f,
				1.00000000000000f, 0.79370052598410f, 0.62996052494744f, 0.50000000000000f, 0.39685026299205f,
				0.31498026247372f, 0.25000000000000f, 0.19842513149602f, 0.15749013123686f, 0.12500000000000f,
				0.09921256574801f, 0.07874506561843f, 0.06250000000000f, 0.04960628287401f, 0.03937253280921f,
				0.03125000000000f, 0.02480314143700f, 0.01968626640461f, 0.01562500000000f, 0.01240157071850f,
				0.00984313320230f, 0.00781250000000f, 0.00620078535925f, 0.00492156660115f, 0.00390625000000f,
				0.00310039267963f, 0.00246078330058f, 0.00195312500000f, 0.00155019633981f, 0.00123039165029f,
				0.00097656250000f, 0.00077509816991f, 0.00061519582514f, 0.00048828125000f, 0.00038754908495f,
				0.00030759791257f, 0.00024414062500f, 0.00019377454248f, 0.00015379895629f, 0.00012207031250f,
				0.00009688727124f, 0.00007689947814f, 0.00006103515625f, 0.00004844363562f, 0.00003844973907f,
				0.00003051757813f, 0.00002422181781f, 0.00001922486954f, 0.00001525878906f, 0.00001211090890f,
				0.00000961243477f, 0.00000762939453f, 0.00000605545445f, 0.00000480621738f, 0.00000381469727f,
				0.00000302772723f, 0.00000240310869f, 0.00000190734863f, 0.00000151386361f, 0.00000120155435f,
				0.00000000000000f /* illegal scalefactor */
		};

		public abstract void read_allocation(Bitstream stream, Header header, Crc16 crc) throws DecoderException;

		public abstract void read_scalefactor(Bitstream stream, Header header);

		public abstract boolean read_sampledata(Bitstream stream);

		public abstract boolean put_next_sample(int channels, SynthesisFilter filter1, SynthesisFilter filter2);
	};

	/**
	 * Class for layer I subbands in single channel mode. Used for single channel
	 * mode and in derived class for intensity stereo mode
	 */
	static class SubbandLayer1 extends Subband {

		// Factors and offsets for sample re-quantization
		public static final float table_factor[] = { 0.0f, (1.0f / 2.0f) * (4.0f / 3.0f), (1.0f / 4.0f) * (8.0f / 7.0f),
				(1.0f / 8.0f) * (16.0f / 15.0f), (1.0f / 16.0f) * (32.0f / 31.0f), (1.0f / 32.0f) * (64.0f / 63.0f),
				(1.0f / 64.0f) * (128.0f / 127.0f), (1.0f / 128.0f) * (256.0f / 255.0f),
				(1.0f / 256.0f) * (512.0f / 511.0f), (1.0f / 512.0f) * (1024.0f / 1023.0f),
				(1.0f / 1024.0f) * (2048.0f / 2047.0f), (1.0f / 2048.0f) * (4096.0f / 4095.0f),
				(1.0f / 4096.0f) * (8192.0f / 8191.0f), (1.0f / 8192.0f) * (16384.0f / 16383.0f),
				(1.0f / 16384.0f) * (32768.0f / 32767.0f) };

		public static final float table_offset[] = { 0.0f, ((1.0f / 2.0f) - 1.0f) * (4.0f / 3.0f),
				((1.0f / 4.0f) - 1.0f) * (8.0f / 7.0f), ((1.0f / 8.0f) - 1.0f) * (16.0f / 15.0f),
				((1.0f / 16.0f) - 1.0f) * (32.0f / 31.0f), ((1.0f / 32.0f) - 1.0f) * (64.0f / 63.0f),
				((1.0f / 64.0f) - 1.0f) * (128.0f / 127.0f), ((1.0f / 128.0f) - 1.0f) * (256.0f / 255.0f),
				((1.0f / 256.0f) - 1.0f) * (512.0f / 511.0f), ((1.0f / 512.0f) - 1.0f) * (1024.0f / 1023.0f),
				((1.0f / 1024.0f) - 1.0f) * (2048.0f / 2047.0f), ((1.0f / 2048.0f) - 1.0f) * (4096.0f / 4095.0f),
				((1.0f / 4096.0f) - 1.0f) * (8192.0f / 8191.0f), ((1.0f / 8192.0f) - 1.0f) * (16384.0f / 16383.0f),
				((1.0f / 16384.0f) - 1.0f) * (32768.0f / 32767.0f) };

		protected int subbandnumber;
		protected int samplenumber;
		protected int allocation;
		protected float scalefactor;
		protected int samplelength;
		protected float sample;
		protected float factor, offset;

		/**
		 * Constructor.
		 */
		public SubbandLayer1(int subbandnumber) {
			this.subbandnumber = subbandnumber;
			samplenumber = 0;
		}

		/**
		 *
		 */
		public void read_allocation(Bitstream stream, Header header, Crc16 crc) throws DecoderException {
			if ((allocation = stream.get_bits(4)) == 15) {
				// CGJ: catch this condition and throw appropriate exception
				throw new DecoderException(DecoderErrors.ILLEGAL_SUBBAND_ALLOCATION, null);
				// cerr << "WARNING: stream contains an illegal allocation!\n";
				// MPEG-stream is corrupted!
			}

			if (crc != null)
				crc.add_bits(allocation, 4);
			if (allocation != 0) {
				samplelength = allocation + 1;
				factor = table_factor[allocation];
				offset = table_offset[allocation];
			}
		}

		/**
		 *
		 */
		public void read_scalefactor(Bitstream stream, Header header) {
			if (allocation != 0)
				scalefactor = scalefactors[stream.get_bits(6)];
		}

		/**
		 *
		 */
		public boolean read_sampledata(Bitstream stream) {
			if (allocation != 0) {
				sample = (float) (stream.get_bits(samplelength));
			}
			if (++samplenumber == 12) {
				samplenumber = 0;
				return true;
			}
			return false;
		}

		/**
		 *
		 */
		public boolean put_next_sample(int channels, SynthesisFilter filter1, SynthesisFilter filter2) {
			if ((allocation != 0) && (channels != OutputChannels.RIGHT_CHANNEL)) {
				float scaled_sample = (sample * factor + offset) * scalefactor;
				filter1.input_sample(scaled_sample, subbandnumber);
			}
			return true;
		}
	};

	/**
	 * Class for layer I subbands in joint stereo mode.
	 */
	static class SubbandLayer1IntensityStereo extends SubbandLayer1 {
		protected float channel2_scalefactor;

		/**
		 * Constructor
		 */
		public SubbandLayer1IntensityStereo(int subbandnumber) {
			super(subbandnumber);
		}

		/**
		 *
		 */
		public void read_allocation(Bitstream stream, Header header, Crc16 crc) throws DecoderException {
			super.read_allocation(stream, header, crc);
		}

		/**
		 *
		 */
		public void read_scalefactor(Bitstream stream, Header header) {
			if (allocation != 0) {
				scalefactor = scalefactors[stream.get_bits(6)];
				channel2_scalefactor = scalefactors[stream.get_bits(6)];
			}
		}

		/**
		 *
		 */
		public boolean read_sampledata(Bitstream stream) {
			return super.read_sampledata(stream);
		}

		/**
		 *
		 */
		public boolean put_next_sample(int channels, SynthesisFilter filter1, SynthesisFilter filter2) {
			if (allocation != 0) {
				sample = sample * factor + offset; // re-quantization
				if (channels == OutputChannels.BOTH_CHANNELS) {
					float sample1 = sample * scalefactor, sample2 = sample * channel2_scalefactor;
					filter1.input_sample(sample1, subbandnumber);
					filter2.input_sample(sample2, subbandnumber);
				} else if (channels == OutputChannels.LEFT_CHANNEL) {
					float sample1 = sample * scalefactor;
					filter1.input_sample(sample1, subbandnumber);
				} else {
					float sample2 = sample * channel2_scalefactor;
					filter1.input_sample(sample2, subbandnumber);
				}
			}
			return true;
		}
	};

	/**
	 * Class for layer I subbands in stereo mode.
	 */
	static class SubbandLayer1Stereo extends SubbandLayer1 {
		protected int channel2_allocation;
		protected float channel2_scalefactor;
		protected int channel2_samplelength;
		protected float channel2_sample;
		protected float channel2_factor, channel2_offset;

		/**
		 * Constructor
		 */
		public SubbandLayer1Stereo(int subbandnumber) {
			super(subbandnumber);
		}

		/**
		 *
		 */
		public void read_allocation(Bitstream stream, Header header, Crc16 crc) throws DecoderException {
			allocation = stream.get_bits(4);
			channel2_allocation = stream.get_bits(4);
			if (crc != null) {
				crc.add_bits(allocation, 4);
				crc.add_bits(channel2_allocation, 4);
			}
			if (allocation != 0) {
				samplelength = allocation + 1;
				factor = table_factor[allocation];
				offset = table_offset[allocation];
			}
			if (channel2_allocation != 0) {
				channel2_samplelength = channel2_allocation + 1;
				channel2_factor = table_factor[channel2_allocation];
				channel2_offset = table_offset[channel2_allocation];
			}
		}

		/**
		 *
		 */
		public void read_scalefactor(Bitstream stream, Header header) {
			if (allocation != 0)
				scalefactor = scalefactors[stream.get_bits(6)];
			if (channel2_allocation != 0)
				channel2_scalefactor = scalefactors[stream.get_bits(6)];
		}

		/**
		 *
		 */
		public boolean read_sampledata(Bitstream stream) {
			boolean returnvalue = super.read_sampledata(stream);
			if (channel2_allocation != 0) {
				channel2_sample = (float) (stream.get_bits(channel2_samplelength));
			}
			return (returnvalue);
		}

		/**
		 *
		 */
		public boolean put_next_sample(int channels, SynthesisFilter filter1, SynthesisFilter filter2) {
			super.put_next_sample(channels, filter1, filter2);
			if ((channel2_allocation != 0) && (channels != OutputChannels.LEFT_CHANNEL)) {
				float sample2 = (channel2_sample * channel2_factor + channel2_offset) * channel2_scalefactor;
				if (channels == OutputChannels.BOTH_CHANNELS)
					filter2.input_sample(sample2, subbandnumber);
				else
					filter1.input_sample(sample2, subbandnumber);
			}
			return true;
		}
	};

}
